Implantable electrical stimulation devices have proven therapeutic in a variety of diseases and disorders. For example, pacemakers and implantable cardiac defibrillators have proven effective in the treatment of cardiac conditions. Spinal cord stimulation systems have been used as a therapeutic modality for the treatment of chronic pain syndromes. Deep brain stimulation has also been useful for treating refractory chronic pain syndromes and has been applied to treat movement disorders and epilepsy. Peripheral nerve stimulation has been used to treat chronic pain syndrome and incontinence, with a number of other applications under investigation. Functional electrical stimulation systems have been applied to restore some functionality to paralyzed extremities in spinal cord injury patients.
Implantable drug delivery systems allow highly concentrated drugs to be delivered to specific sites. This site specific delivery can result in reduced side effects, improved quality of life, and, in some cases, may extend life. Such drug delivery systems include both programmable pumps and constant flow pumps. Examples of such systems include intrathecal drug delivery for the treatment of chronic intractable pain; delivery of baclofen for the treatment of spasticity; site specific delivery of drugs for the treatment of cancer, and site specific insulin delivery for the management of diabetes.
One disadvantage of these devices is that the electrode lead or drug catheter may migrate within the body. Migration may result in failure of the therapy or cause unwanted side effects. For example, some nerves are located next to or within muscles that may cause movement of the lead or catheter. Actuation of limbs may exert unequal pressures which can also cause migration. Some nerves are near or within firm, but lubricious, tissue. For example, the vagus nerve runs through the carotid sheath in the neck and is surrounded by a number of muscles which can cause migration of an implanted lead or catheter. The firm, lubricious carotid sheath may offer little adhesion to a lead or catheter and actuation of the surrounding neck muscles may cause significant migration especially during the period immediately following implantation.